Xwayland DPI increases on hotplug

[Simon Ser]

Hi all,

Whenever I plug/unplug an output on my compositor, Xwayland's DPI value
increases. I've noticed a bug a long time ago in wlroots, and realized
I can reproduce in weston too.

For instance, when starting `weston --xwayland` this is the DPI:

> xdpyinfo | grep dots
  resolution:    96x96 dots per inch

When I plug an output:

  resolution:    114x114 dots per inch

When I unplug it:

  resolution:    131x131 dots per inch

And this is going crazy when the output is a virtual window and I
resize it:

  resolution:    -2147483648x-2147483648 dots per inch

This is causing issues with some X11 clients (for instance dmenu).

However, both the mode size and the physical size are still correct. Do
you have any idea where this DPI value is coming from?

Thanks,
---
Simon Ser
https://emersion.fr